Fuel injection system for internal combustion engine

ABSTRACT

This fuel injection system for internal combustion engines includes first means for generating a DC voltage proportional to the weight flow rate of air taken into an engine, second means for generating a sawtooth voltage which is synchronized with the working cycle of the engine and whose slope varies with the rotational speed of the engine, third means for comparing the output voltages of said first and second means and generating a pulse corresponding to the amount of fuel required for each engine cylinder per operating cycle of the engine, and at least one electromagnetic valve operable in response to a pulse generated by said third means.

United States Patent [1 1 [111 3,835,820 Fujisawa Sept. 17, 1974 [54] FUEL INJECTION SYSTEM FOR INTERNAL 3,660,689 5/1972 Oishi 123/32 EA O US IO ENGINE 3,683,870 8/1972 Jackson l23/32 EA [75] Inventor: Hideya Fujisawa, Kariya, Japan [73] Assignee: Nipponsenso Co. Ltd., Aichi-ken,

Japan [22] Filed: June 16, 1972 [21] Appl. No.: 263,618

[30] Foreign Application Priority Data June 17, 1971 Japan 46-43607 [52] US. Cl 123/32, 123/119 R, 123/140 MC [51] Int. Cl. F02m 51/02, F02d 5/02 [58] Field of Search..... 123/119 R, 32 EA, 140 MC [56] References Cited UNITED STATES PATENTS 3,456,628 7/1969 Bassot 123/119 R 3,612,009 10/1971 Kamazuka 123/32 EA 3,636,931 l/l972 Suda et a1. 123/119 R 3,645,240 2/1972 Monpetit 123/32 EA 3,653,365 4/1972 Monpetit 123/119 R Primary ExaminerLaurence M. Goodridge Assistant ExaminerCort R. Flint Attorney, Agent, or FirmCushman, Darby & Cushman [5 7 ABSTRACT This fuel injection system for internal combustion engines includes first means for generating a DC voltage proportional to the weight flow rate of air taken into an engine, second means for generating a sawtooth voltage which is synchronized with the working cycle of the engine and whose slope varies with the rotational speed of the engine, third means for comparing the output voltages of said first and second means and generating a pulse corresponding to the amount of fuel required for each engine cylinder per operating cycle of the engine, and at least one electromagnetic valve operable in response to a pulse generated by said third means.

6 Claims, 17 Drawing Figures PRESSURE RELIEF 1 VALVE 48 ELECTROMAGNE- A C no GEI\ERATOR 3| VALVE ACTUAT- 40 4| ms CRCUIT 39 FLlP- 38 43 FLOP VOLTAGE TRANSDUCER VOLTAGE PRESSURE- 28 29 EAIENIEDSEPIYW 3.885320 sum -1 ur e PRESSURE FUEL I RELIEF \U VALVE BUTOR a 8 s I r I 1 LP '1 "2);; IO

A l3 l4 l2 X S. 34 V 6% 4 r A --|5 9 9i 9 IP 9 23 91. I?6 16 48 HECTROITAG'NEI I AC TIC GENERATOR VALVE ACTUAT- 40 ms CIRCUIT ,39 4| lg mp- 35 FLOP M v ouAGE TRANSDUCER PRESSRE- fi VOLTAGE PAIENIEIJ SEP 1 71914 SHEET 2 OF 6 FIG FIG

PATENIEDSEPITW 3.885.820

SHEEI 3 0F 6 F I G 4 QA AP AIR FLOW RATE PRESSURE. DIFFERENCE F l G 6 TEMPERATURE N ENGINE RF. M

IIIEIIIIIIIIIIT III I amsiazo SHEET 14 UF 6 F I G 9 OUTPUT OF A.C GENERATOR 36 A A F l G l0 OUTPUT 0F CCWIRATOR 40' J l I L I F l G ll I lhPUT To NAND CIRCUIT 64 IL L L W Y K SET SIGNAL F I G l2 OUTPUT OF M U NAND CIRCUIT.65

F G i UTPUT 0F 0 l COEFFICIENT m MULTIPLIER 44 OUTPU OF INTEGRATOR as I i FIG I4 i i I [OUTPUT OF COMPARATOR 43 REsET SIGNAL PAIENIED 3335.820

' sum 6 or 6 FIG.|6

9 AIR THROTTLE VALVE OPENING FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronically controlled fuel injection system for an external-ignition type internal combustion engine employing electromagnetically operated fuel injection valves and adapted to control the duration of the opening of the electromagnetic valves in accordance with the time width of voltage pulses to measure the quantity of fuel delivered.

2. Description of the Prior Art In known fuel injection systems of this type, the amount of air per cycle of an engine is determined in accordance with the pressure in the inlet pipe of the engine, so that the quantity of fuel to be delivered is measured according to this pressure and then fed to the engine in synchronization with the revolutions of the engine. The systems of this kind are generally known as the speed-density type.

While it is prerequisite for the conventional fuel injection systems of the above type that the pressure in the inlet pipe and the amount of air per cycle of the engine exactly correspond with each other, this functional relation in fact varies depending on the number of revolutions of the engine and it is therefore necessary to correct in respect of the revolutions of the engine. However, it is very difficult to effect this correction in respect of the engine revolutions and there has still existed a need for improvement in this respect. Thus, a serious drawback of the conventional systems is that it is difficult to meet the correct mixing ratio over a certain range of engine revolutions.

SUMMARY OF THE INVENTION To solve the foregoing difficulty, it is an object of the present invention to provide a fuel injection system for internal combustion engines, in which the flow rate of air taken into an engine per unit time is measured, so that the quantity of fuel per cycle of the engine, i.e., the duration of the opening of the electromagnetic valves is controlled according to the measured flow rate of the air taken and the revolutions of the engine to thereby accurately meter the fuel quantity to give the accurately adjusted air-fuel ratio.

The above and other objects, features and advantages of the present invention will be readily apparent from the following description of a preferred embodiment of the present invention taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a block diagram showing an embodiment of the fuel injection system for internal combustion engines according to the present invention.

FIG. 2 is a longitudinal sectional view of an air cleaner and an air flow meter of the fuel injection system of FIG. 1.

FIG. 3 is a cross-sectional view of an air flow measuring element of the air flow meter shown in FIG. 2.

FIG. 4 is a graph showing the relationship between the flow rate of air through the air flow meter and the pressure difference.

FIG. 5 is a characteristic diagram of the output voltage of a differential pressure-voltage transducer.

FIG. 6 is a schematic diagram of a coefficient multiplier FIG. 7 is a graph showing the relationship between the temperature and the ratio between the input and output voltages of the coefficient multiplier of FIG. 6.

FIG. 8 is a characteristic diagram of the output voltage of an engine revolution-voltage transducer.

FIGS. 9, 10, 11, l2, l3 and 14 are diagrams using the same time base as the abscissa for explaining the voltage signals and switching operations at various parts of the system of FIG. 1.

FIG. 15 is a schematic diagram showing an embodiment of the electric circuity of the electric control section of the system illustrated inn FIG. 1.

FIG. 16 is a schematic diagram of a coefficient multiplier operatively associated with an air flow rate adjuster.

FIG. 17 is a graph showing the relationship between the input-output ratio of the coefficient multiplier and the opening of an air throttle valve.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention will now be explained with reference to the preferred embodiment illustrated in the accompanying drawing. Referring first to FIG. 1, numeral 1 designates a fuel tank, 2 a fuel feed pump, 3 a pressure relief valve, 4 a fuel distributor. The fuel feed pump 2 is driven by an electric motor (not shown) to draw out fuel from the fuel tank 1. A portion of the fuel thus drawn out is returned to the fuel tank 1 by the pressure relief valve 3 through a return line 5, thus maintaining the pressure in fuel lines 6 and 7 and the fuel distributor 4 at a constant pressure. Fuel injection pipes 8 are connected to the fuel distributor 4 to feed the fuel to electromagnetic valves 9. The fuel pressure in the electromagnetic valves 9 is maintained at the same constant value as the fuel pressure in the distributor 4. The electromagnetic valves 9 are mounted on an inlet pipe 11 of an engine 10. Air taken into the engine 10 is fed via an air cleaner 12, an air flow meter 13, an air flow rate adjuster l4 and through the inlet pipe 11. The amount of air supplied to the engine 10 is regulated according to the opening of an air throttle valve 15 of the air flow rate adjuster 14, and the air throttle valve 15 is linked to an accelerator pedal 16 by a suitable linkage so that the air quantity is regulated through the manipulation of the accelerator pedal 16 by the driver. The quantity of fuel to be delivered is controlled according to the amount of air supplied to the engine 10 and the metering of the fuel is effected in accordance with the time width of a voltage which energizes the electromagnetic valves 9, i.e., the duration of the opening of the electromagnetic valves 9. The air flow meter 13 is mounted downstream of the air cleaner 12 and it is constructed as shown in FIG. 2. In this figure, numeral 17 designates an air cleaner case having an air inlet port 18, 19 an air cleaner element, 20 a cover secured to the air cleaner case 17 by a known means which is not shown. As shown by arrows, the air to be drawn in passes through the air cleaner element 9 and through an air flow rate measuring element 21. The air flow rate measuring element 21 is secured to a casing 22 attached to the air cleaner case 17 and the casing 22 is provided with air pressure inlet pipes 22A and 228 formed to open respectively at the upstream and downstream of the air flow rate measuring element 21. The air flow rate measuring element 21 comprises, as shown in FIG. 3, a large number of very small tubes parallel to the axis. So far as the Reynolds number which is expressed according to the velocity of air flowing through this small tube, the hydraulic diameter of the tube and the dynamic viscosity coefficient of the air, remains less than about 300, the air flow in the tube is laminar. It is thus known that thepressure differenceacross the tube is proportional to the velocity of the air flow through the tube. Since the number of the small tubes is known, there is a proportional relationship between the total volumetric flow rate Q A cc/sec of the air flowing through the entire tubes and the pressure difference AP Kg/cm across the air flow rate measuring element 21 as shown in FIG. 4. The pressure difference AP Kg/cm is measured by a differential pressure-voltage transducer 23 connected to the air pressure inlet pipes 22A and 22B, the transducer consisting of for example a known diaphragm operated type transducer and adapted to convert the pressure difference AP Kg/cm into an output voltage B in volts as shown in FIG. 5. In summary, the volumetric flow rate QA cclsec of air taken into an engine can be measured in terms of a voltage E, in volts. The voltage E (V) is applied to an electric line 24 through which it is coupled to the coefficient multiplier 25. The coefficient multiplier 25 is constructed as shown in FIG. 6 so that the resistance of an electrical resistor 27 is varied according to the position of the forward end portion of a temperature-position transducer 26 consisting of for example a bimetal strip whose shape changes with temperature. If the voltage E is applied to a terminal 28 of the resistor 27, an output voltage E (V) is produced at the other terminal 29 at a temperature 1C. Since the voltage E (v) has a value proportional to the volumetric flow rate of air fed to the engine as previously explained, if the coefficient multiplier 25 is related to the temperature of the air drawn, its inputoutput voltage raatio E,,' /E,, varies with the temperature of the air drawn as shown in FIG. 7. And this represents a correction required for the quantity of the air drawn.

Numeral 30 designates a pressure-voltage transducer of the type known in the art which measures and converts the atmospheric pressure into a voltage. The product of the voltage E, (V) and the output voltage of the pressure-voltage transducer 30 which is related to the atmospheric pressure is delivered to an output line 32. The output voltage E (V) applied on the output line 32 is proportional to the weight flow rate of the air supplied to the engine. Numeral 33 designates a rotary shaft which rotates atthe same revolutions as the engine and numeral 34 designates a speed reducing shaft that rotates at a speed which is one half the revolutions of the engine 10. An AC voltage generator 36 of a known type is mechanically connected to the speed reducing shaft 36. The output of the AC voltage generator 36 is supplied to a revolution voltage transducer 35 consisting of, as shown by way of example in FIG. 15, a diode 49 and a capacitor 50 and the characteristic of its output voltage E-(V) is proportional to the engine revolutions N rpm as shown in FIG. 8. The output voltage E-(V) is applied to an electrical line 37 and it is then coupled to an integrator 38. On the other hand,

the output voltage of the AC voltage generator 36 has a period of one cycle per revolution of the speed reducing shaft 34 reversing its polarity with respect to 21 reference voltage 0(V) as shown in FIG. 9. This AC voltage is applied to a comparator 40 through a line 39. The comparator 40 compares this AC voltage with the reference voltage 0(V) so that it produces a 1 signal when the AC voltage is greater than the reference voltage and a 0 signal is produced when the former is smaller than the latter, thus delivering the output signal shown in FIG. 10 to a line 41. The integrator 38 comprises, as shown by way of example in FIG. 15, resistors 51, 52, 53, 54, and 56, capacitors 57, 58 and 59, diodes 60 and 61, an operational amplifier 62 and a transistor 63. A flip-flop 31 is connected to the integrator 38 to place the latter in its integrating and reset states. As shown by way of example in FIG. 15, the flip-flop 31 comprises NAND circuits 64 and 65 and it is operated when it receives a set signal as shown in FIG. 11 from a differentiation circuit which comprises, as shown in FIG. 15, a capacitor 66 and a resistor 67 and to which the output signal of the comparator 40 is applied. The application of this set signal to the flip-flop 31 causes the NAND circuit 64 to change its state changing its output from O to I. This causes the output of the NAND circuit 65 to change from 1 to 0 so that the transistor 63 of the integrator 38 passes from its conducting state to its non-conducting state. Consequently, the integrator 38 starts its integrating operation and its output forms the sawtooth waveform as shown in FIG. 13. The slope of this sawtooth waveform is governed by the output of the revolution-voltage transducer 35 connected to the integrator 38. The output voltage of the integrator 38 is applied to a comparator 43. As previously explained, the voltage E (V) proportional to the weight flow rate of the air taken into the engine is applied to the line 32 and the line 32 is also connected to a coefficient multiplier 44. As shown in FIG. 16, the coefficient multiplier 44 comprises an electrical resistor operatively associated with the air flow rate adjuster 14 so that it receives the voltage E (V) at its input terminal 45 and produces at its output terminal 46 a voltage E corrected for the opening 0 of the air throttle valve 15. The relationship between the opening 0 of the air throttle valve and the input-output voltage ratio E IE of the coefficient multiplier 44 shown in FIG. 17 is determined by the construction of the resistor 47 relative to the throttle opening 6.

It will be thus understood that the voltage E (V) produced at the output terminal 46 is in fact the voltage E proportional to the weight flow rate of the air actually supplied to the engine, which is corrected as if more air were supplied to the engine.

The output voltage E,;' (V) of the coefficient multiplier 44 and the output of the integrator 38 are then applied to the comparator 43 through resistors 68 and 72 so that the two input signals are compared as shown in FIG. 13. When the voltage E (V) becomes greater than the sawtooth wave output voltage of the integrator 38, the comparator 43 changes its output and thus produces, as shown in FIG. 14, a reset signal which is delivered to an output line 42 of the comparator 43. The signal that flows through the output line 42 is used as a control voltage for actuating the NAND circuit 65 of the flip-flop 31. In other words, the output of the NAND circuit 65 changes from O to 1. Consequently,

the integrator 38 terminates its integrating operation and discharges and the comparator 43 also immediately changes its state returning to the initial condition. On the other hand, the output of the NAND circuit 65 is connected to an electromagnetic valve actuating circuit 48 comprising, as shown by way of example in FIG. 15, resistors 69, 70, 71, 72 and 73 and transistors 74 and 75. Thus, as shown in FIG. 12, the electromagnetic valve 9 is energized from a power source 78 and re mains open for a time duration 1- during which time the output of the NAND circuit 65 remains in the 1 state.

As previously explained, the energizing time duration 1' is proportional to the quantity of fuel fed to the engine by the electromagnetic valve 9. The energizing time duration 7 is determined by the output of the coefficient multiplier 44, i.e., the voltage E (V) proportional to the weight flow rate of the air taken and the sawtooth wave output voltage of the integrator 38. Thus, this time duration is proportional to the quantity of fuel fed in parts according to a timed sequence in synchronization with the revolutions of an engine and in proper balance with the weight flow rate of the air supplied to the engine.

While the above description of the embodiment has been made in connection with only one engine cylinder, so many electromagnetic valves 9 as there are engine cylinders may be provided in parallel so as to simultaneously inject fuel into all the cylinders. It is also possible to inject fuel into the cylinders one at a time or in suitable groups by adding the necessary number of the circuits shown in FIG. excepting the differential pressure-voltage transducer 23, coefficient multiplier 25, pressure-voltage transducer 30 and coefficient multiplier 44.

It should be apparent from the foregoing description that in the fuel injection system for internal combustion engines provided according to the present invention, the volumetric flow rate of air drawn into an engine is converted into and detected as a voltage which is then corrected for the external temperature and atmospheric pressure to produce a voltage proportional to the weight flow rate of air supplied to the engine, while the output of the flip-flop 31 is related to the output voltage of the revolution-voltage transducer 35 which is proportional to the revolutions of the engine 10 and integrated in synchronization with the rotation of the engine 10 producing a sawtooth wave voltage. The voltage proportional to the weight flow rate and the sawtooth wave voltage are then compared and the result of this comparison is applied to the flip-flop 31 so that the output of the flip-flop 31 is employed to energize the electromagnetic valve 9. There is thus an excellent feature in that the quantity of fuel that suits the weight flow rate of air supplied to an engine can be measured and supplied in timed sequence to each engine cylinder within each operating cycle of the engine, thereby eliminating the need for a correction for the engine revolutions as required in the conventional speed-density type systems.

Moreover, since the weight flow rate of air drawn is increased apparently in relation to the opening of the air throttle valve 15, the air-fuel ratio can be continuously adjusted in accordance with the opening of the air throttle valve 15 so that the output mixture may be obtained at near full throttle.

I claim:

l. A fuel injection system for internal combustion engines comprising,

means for generating a DC voltage proportional to the weight flow rate of air taken into an engine,

means for generating a sawtooth wave voltage which is synchronized with the working cycle of the engine and whose slope varies in accordance with the rotational speed of the engine,

pulse generating means connected in circuit with said two means for comparing the output voltages of said two means for comparing the output voltages of said two means to produce a pulse corresponding to the quantity of fuel required for each cylinder of the engine per operating cycle thereof, and

at least one electromagnetic valve connected in circuit with said pulse generating means and operable in response to said pulse generated by said pulse generating means,

wherein the first mentioned generating means includes an air flow-voltage transducer comprises an air flow rate measuring element mounted downstream of an air cleaner in the inlet pipe of the en gine and composed of a plurality of small tubes arranged in parallel in the direction of flow of the air in said inlet pipe, air pressure inlet pipes opened respectively at the upstream and downstream sides of said air flow rate measuring element to receive the air pressures at said upstream and downstream sides, and a differential pressure-voltage transducer connected to said air pressure inlet pipes for detecting the pressure difference between the air pressures induced through said air pressure inlet pipes to generate a voltage corresponding to said pressure difference.

2.A fuel injection system for internal combustion engines comprising,

a first means for generating signals responsive to engine revolution,

pulse generating means connected in circuit with said first means for generating a pulse synchronized with the working cycle of an associated engine,

an engine revolution-voltage transducer connected in circuit with said first means for generating a DC voltage, the value of which is proportional to the engine revolution,

a flip-flop circuit having two input terminals, one of said input terminals being connected in circuit with said pulse generating means, for succeeding to generate an output signal when the pulse of said pulse generating means is applied,

an integrator circuit connected in circuit with said flip-flop circuit and said engine revolution-voltage transducer for generating a sawtooth wave voltage which is synchronized with the generation of the output signal from said flip-flop circuit and whose slope varies in accordance with the value of said DC voltage,

a second means for generating a voltage signal responsive to the weight flow rate of the air taken into the engine,

a comparator connected in circuit at the input terminals thereof with said integrator circuit and said second means and at the output terminal thereof with the other terminal of said flip-flop circuit for comparing a voltage signal of said second means with said sawtooth wave voltage and generating an output signal for stopping said output signal from said flip-flop circuit, and

an electromagnetic valve means connected in circuit with said flip-flop circuit for supplying fuel to the engine during the time duration when the output signal of said flip-flop circuit is generating,

wherein said second means comprises an air flow rate-voltage transducer for generating an output voltage directly proportional to the weight flow rate of the air taken into the engine, a temperature coefficient multiplier connected in circuit with said air flow rate-voltage transducer for generating an output voltage representative of the output voltage of said air flow rate-voltage transducer modified in accordance with the temperature of the air induced, an atmospheric pressure detector connected in circuit with said temperature coefficient multiplier for correcting the output voltage of said temperature coefficient multiplier in accordance with the value of the atmospheric pressure and generating an output voltage, and an air throttle valve opening coefficient multiplier connected in circuit with said atmospheric pressure detector for correcting the output voltage of said atmospheric pressure detector in accordance with the opening of said air throttle valve any generating an output signal to said comparator, and

wherein said air flow rate-voltage transducer comprises an air flow rate measuring element mounted downstream of an air cleaner in the inlet pipe of the engine and composed of a plurality of small tubes arranged in parallel in the direction of flow of the air in said inlet pipe, air pressure inlet pipes opened respectively at the upstream and downstream sides of said air flow rate measuring element to receive the air pressures at said upstream and downstream sides, and a differential pressurevoltage transducer connected to said air pressure inlet pipes for detecting the pressure difference between the air pressures induced through said air pressure inlet pipes to generate a voltage corresponding to said pressure difference.

3. A fuel injection system for internal combustion engines comprising,

a first means for generating signals responsive to engine revolution,

pulse generating means connected in circuit with said first means for generating a pulse synchronized with the working cycle of an associated engine,

an engine revolution-voltage transducer connected in circuit with said first means for generating a DC voltage, the value of which is proportional to the engine revolution,

a flip-flop circuit having two input terminals, one of said input terminals being connected in circuit with said pulse generaating means, for succeeding to generate an output signal when the pulse of said pulse generating means is applied,

anintegrator circuit connected in circuit with said flip-flop circuit and said engine revolution-voltage transducer for generating a sawtooth wave voltage which is synchronized with the generation of the nals thereof with said integrator circuit and said second means and at the output terminal thereof with the other terminal of said flip-flop circuit for comparing a voltage signal of said second means with said sawtooth wave voltage and generating an output signal for stopping said output signal from said flip-flop circuit, and

an electromagnetic valve means connected in circuit with said flip-flop circuit for supplying fuel to the engine during the time duration when the output signal of said flip-flop circuit is generating,

wherein said second means comprises an air flow rate-voltage transducer for generating an output voltage directly proportional to the weight flow rate of the air taken into the engine, a temperature coefficient multiplier connected in circuit with said air flow rate-voltage transducer for generating an output voltage representative of the output voltage of said air flow rate-voltage transducer modified in accordance with the temperature of the air induced, an atmospheric pressure detector connected in circuit with said temperature coefficient multiplier for correcting the output voltage of said temperature coefficient multiplier in accordance with the value of the atmospheric pressure and generating an output voltage, and an air throttle valve opening coefficient multiplier connected in circuit with said atmospheric pressure detector for correcting the output voltage of said atmospheric pressure detector in accordance with the opening of said air throttle valve and generating an output signal to said comparator, and

wherein said temperature coefficient multiplier comprises a bimetal adapted to make a predetermined amount of mechanical displacement with a change in temperature, and an electrical resistor connected with said bimetal strip whose resistance value changes in accordance with the mechanical displacement of said bimetal strip, whereby the output voltage of said air flow rate-voltage transducer is corrected in accordance with a change in the resistance value of said electrical resistor to produce an output voltage.

4. A fuel injection system for internal combustion engines comprising,

means for generating a DC voltage proportional to the weight flow rate of air taken into an engine,

means for generating a sawtooth wave voltage which is synchronized with the working cycle of the engine and whose slope varies in accordance with the rotational speed of the engine,

pulse generating connected in circuit with said two means for comparing the output voltages of said two means to produce a pulse corresponding to the quantity of fuel required for each cylinder of the engine per operating cycle thereof, and

at least one electromagnetic valve connected in circuit with said pulse generating means and operable in response to said pulse generated by said pulse generating means,

wherein the first mentioned generating means includes an air flow rate-voltage transducer for generating an output voltage directly proportional to the weight flow rate of the air taken into the engine, a temperature coefficient multiplier connected in circuit with said air flow rate-voltage transducer for generating an output voltage representative of the output voltage of said air flow ratevoltage transducer modified in accordance with the temperature of the air induced, an atmospheric pressure detector connected in circuit with said temperature coefficient multiplier for correcting the output voltage of said temperature coefficient multiplier in accordance with the value of the atmospheric pressure and generating an output voltage, and an air throttle valve opening coefficient multiplier connected in circuit with said atmospheric pressure detector for correcting the output voltage of said atmospheric pressure detector in accordance with the opening of said air throttle valve any generating an output signal to said comparator, and

wherein said air flow rate-voltage transducer comprises an air flow rate measuring element mounted downstream of an air cleaner in the inlet pipe of the engine and composed of a plurality of small tubes arranged in parallel in the direction of flow of the air in said inlet pipe, air pressure inlet pipes opened respectively at the upstream and downstream sides of said air flow rate measuring element to receive the air pressures at said upstream and downstream sides, and a differential pressure-voltage transducer connected to said air pressure inlet pipes for detecting the pressure difference between the air pressures induced through said air pressure inlet pipes to generate a voltage corresponding to said pressure difference.

5. A fuel injection system according to claim 4, wherein said temperature coefficient multiplier comprises a bimetal adapted to make a predetermined amount of mechanical displacement with a change in temperature, and an electrical resistor connected with said bimetal strip whose resistance value changes in accordance with the mechanical displacement of said bimetal strip, whereby the output voltage of said air flow rate-voltage transducer is corrected in accordance with a change in the resistance value of said electrical resistor to produce an output voltage.

6. A fuel injection system for internal combustion engines comprising,

means for generating a DC voltage proportional to the weight flow rate of air taken into an engine,

means for generating a sawtooth wave voltage which is synchronized with the working cycle of the engine and whose slope varies in accordance with the rotational speed of the engine,

pulse generating connected in circuit with said two means for comparing the output voltages of said two means to produce a pulse corresponding to the quantity of fuel required for each cylinder of the engine per operating cycle thereof, and

at least one electromagnetic valve connected in circuit with said pulse generating means and operable in response to said pulse generated by said pulse generating means,

wherein the first mentioned generating means includes an air flow rate-voltage transducer for generating an output voltage directly proportional to the weight flow rate of the air taken into the engine, a temperature coefi'icient multiplier connected in circuit with said air flow rate-voltage transducer for generating an output voltage representative of the output voltage of said air flow ratevoltage transducer modified in accordance with the temperature of the air induced, an atmospheric pressure detector connected in circuit with said temperature coefficient multiplier for correcting the output voltage of said temperature coefficient multiplier in accordance with the value of the atmospheric pressure and generating an output voltage, and an air throttle valve opening coefficient multiplier connected in circuit with said atmospheric pressure detector for correcting the output voltage of said atmospheric pressure detector in accordance with the opening of said air throttle valve and generating an output signal to said signal to said comparator, and

wherein said temperature coefiicient multiplier comprises a bimetal adapted to make a predetermined amount of mechanical displacement with a change in temperature, and an electrical resistor connected with said bimetal strip whose resistance value changes in accordance with the mechanical displacement of said bimetal strip, whereby the output voltage of said air flow rate-voltage transducer is corrected in accordance with a change in the resistance value of said electrical resistor to produce an output voltage.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3: 35, Dated September 17, 197

Inventor( Hideya Fujisawa It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

a ea

Item [73], change "Nipponsenso 00., Ltd. to

--Nippondenso 00., Ltd.

Column 6 Claim 1, Lines 11 and 12 delete:

for comparing the output voltages of said two means" Signed and sealed this 18th day of March 1975.

(SEAL) Attest C MARSHALL DANN RUTH C. MASON I Commissioner of Patents Attesting Officer and Trademarks 

1. A fuel injection system for internal combustion engines comprising, means for generating a DC voltage proportional to the weight flow rate of air taken into an engine, means for generating a sawtooth wave voltage which is synchronized with the working cycle of the engine and whose slope varies in accordance with the rotational speed of the engine, pulse generating means connected in circuit with said two means for comparing the output voltages of said two means for comparing the output voltages of said two means to produce a pulse corresponding to the quantity of fuel required for each cylinder of the engine per operating cycle thereof, and at least one electromagnetic valve connected in circuit with said pulse generating means and operable in response to said pulse generated by said pulse generating means, wherein the first mentioned generating means includes an air flow-voltage transducer comprises an air flow rate measuring element mounted downstream of an air cleaner in the inlet pipe of the engine and composed of a plurality of small tubes arranged in parallel in the direction of flow of the air in said inlet pipe, air pressure inlet pipes opened respectively at the upstream and downstream sides of said air flow rate measuring element to receive the air pressures at said upstream and downstreAm sides, and a differential pressure-voltage transducer connected to said air pressure inlet pipes for detecting the pressure difference between the air pressures induced through said air pressure inlet pipes to generate a voltage corresponding to said pressure difference.
 2. A fuel injection system for internal combustion engines comprising, a first means for generating signals responsive to engine revolution, pulse generating means connected in circuit with said first means for generating a pulse synchronized with the working cycle of an associated engine, an engine revolution-voltage transducer connected in circuit with said first means for generating a DC voltage, the value of which is proportional to the engine revolution, a flip-flop circuit having two input terminals, one of said input terminals being connected in circuit with said pulse generating means, for succeeding to generate an output signal when the pulse of said pulse generating means is applied, an integrator circuit connected in circuit with said flip-flop circuit and said engine revolution-voltage transducer for generating a sawtooth wave voltage which is synchronized with the generation of the output signal from said flip-flop circuit and whose slope varies in accordance with the value of said DC voltage, a second means for generating a voltage signal responsive to the weight flow rate of the air taken into the engine, a comparator connected in circuit at the input terminals thereof with said integrator circuit and said second means and at the output terminal thereof with the other terminal of said flip-flop circuit for comparing a voltage signal of said second means with said sawtooth wave voltage and generating an output signal for stopping said output signal from said flip-flop circuit, and an electromagnetic valve means connected in circuit with said flip-flop circuit for supplying fuel to the engine during the time duration when the output signal of said flip-flop circuit is generating, wherein said second means comprises an air flow rate-voltage transducer for generating an output voltage directly proportional to the weight flow rate of the air taken into the engine, a temperature coefficient multiplier connected in circuit with said air flow rate-voltage transducer for generating an output voltage representative of the output voltage of said air flow rate-voltage transducer modified in accordance with the temperature of the air induced, an atmospheric pressure detector connected in circuit with said temperature coefficient multiplier for correcting the output voltage of said temperature coefficient multiplier in accordance with the value of the atmospheric pressure and generating an output voltage, and an air throttle valve opening coefficient multiplier connected in circuit with said atmospheric pressure detector for correcting the output voltage of said atmospheric pressure detector in accordance with the opening of said air throttle valve any generating an output signal to said comparator, and wherein said air flow rate-voltage transducer comprises an air flow rate measuring element mounted downstream of an air cleaner in the inlet pipe of the engine and composed of a plurality of small tubes arranged in parallel in the direction of flow of the air in said inlet pipe, air pressure inlet pipes opened respectively at the upstream and downstream sides of said air flow rate measuring element to receive the air pressures at said upstream and downstream sides, and a differential pressure-voltage transducer connected to said air pressure inlet pipes for detecting the pressure difference between the air pressures induced through said air pressure inlet pipes to generate a voltage corresponding to said pressure difference.
 3. A fuel injection system for internal combustion engines comprising, a first means for generating signals responsive to engine revolution, pulse generating means connected in circuit with said first means for geneRating a pulse synchronized with the working cycle of an associated engine, an engine revolution-voltage transducer connected in circuit with said first means for generating a DC voltage, the value of which is proportional to the engine revolution, a flip-flop circuit having two input terminals, one of said input terminals being connected in circuit with said pulse generaating means, for succeeding to generate an output signal when the pulse of said pulse generating means is applied, an integrator circuit connected in circuit with said flip-flop circuit and said engine revolution-voltage transducer for generating a sawtooth wave voltage which is synchronized with the generation of the output signal from said flip-flop circuit and whose slope varies in accordance with the value of said DC voltage, a second means for generating a voltage signal responsive to the weight flow rate of the air taken into the engine, a comparator connected in circuit at the input terminals thereof with said integrator circuit and said second means and at the output terminal thereof with the other terminal of said flip-flop circuit for comparing a voltage signal of said second means with said sawtooth wave voltage and generating an output signal for stopping said output signal from said flip-flop circuit, and an electromagnetic valve means connected in circuit with said flip-flop circuit for supplying fuel to the engine during the time duration when the output signal of said flip-flop circuit is generating, wherein said second means comprises an air flow rate-voltage transducer for generating an output voltage directly proportional to the weight flow rate of the air taken into the engine, a temperature coefficient multiplier connected in circuit with said air flow rate-voltage transducer for generating an output voltage representative of the output voltage of said air flow rate-voltage transducer modified in accordance with the temperature of the air induced, an atmospheric pressure detector connected in circuit with said temperature coefficient multiplier for correcting the output voltage of said temperature coefficient multiplier in accordance with the value of the atmospheric pressure and generating an output voltage, and an air throttle valve opening coefficient multiplier connected in circuit with said atmospheric pressure detector for correcting the output voltage of said atmospheric pressure detector in accordance with the opening of said air throttle valve and generating an output signal to said comparator, and wherein said temperature coefficient multiplier comprises a bimetal adapted to make a predetermined amount of mechanical displacement with a change in temperature, and an electrical resistor connected with said bimetal strip whose resistance value changes in accordance with the mechanical displacement of said bimetal strip, whereby the output voltage of said air flow rate-voltage transducer is corrected in accordance with a change in the resistance value of said electrical resistor to produce an output voltage.
 4. A fuel injection system for internal combustion engines comprising, means for generating a DC voltage proportional to the weight flow rate of air taken into an engine, means for generating a sawtooth wave voltage which is synchronized with the working cycle of the engine and whose slope varies in accordance with the rotational speed of the engine, pulse generating connected in circuit with said two means for comparing the output voltages of said two means to produce a pulse corresponding to the quantity of fuel required for each cylinder of the engine per operating cycle thereof, and at least one electromagnetic valve connected in circuit with said pulse generating means and operable in response to said pulse generated by said pulse generating means, wherein the first mentioned generating means includes an air flow rate-voltage transducer for generating an output voltage directly proportional to the weIght flow rate of the air taken into the engine, a temperature coefficient multiplier connected in circuit with said air flow rate-voltage transducer for generating an output voltage representative of the output voltage of said air flow rate-voltage transducer modified in accordance with the temperature of the air induced, an atmospheric pressure detector connected in circuit with said temperature coefficient multiplier for correcting the output voltage of said temperature coefficient multiplier in accordance with the value of the atmospheric pressure and generating an output voltage, and an air throttle valve opening coefficient multiplier connected in circuit with said atmospheric pressure detector for correcting the output voltage of said atmospheric pressure detector in accordance with the opening of said air throttle valve any generating an output signal to said comparator, and wherein said air flow rate-voltage transducer comprises an air flow rate measuring element mounted downstream of an air cleaner in the inlet pipe of the engine and composed of a plurality of small tubes arranged in parallel in the direction of flow of the air in said inlet pipe, air pressure inlet pipes opened respectively at the upstream and downstream sides of said air flow rate measuring element to receive the air pressures at said upstream and downstream sides, and a differential pressure-voltage transducer connected to said air pressure inlet pipes for detecting the pressure difference between the air pressures induced through said air pressure inlet pipes to generate a voltage corresponding to said pressure difference.
 5. A fuel injection system according to claim 4, wherein said temperature coefficient multiplier comprises a bimetal adapted to make a predetermined amount of mechanical displacement with a change in temperature, and an electrical resistor connected with said bimetal strip whose resistance value changes in accordance with the mechanical displacement of said bimetal strip, whereby the output voltage of said air flow rate-voltage transducer is corrected in accordance with a change in the resistance value of said electrical resistor to produce an output voltage.
 6. A fuel injection system for internal combustion engines comprising, means for generating a DC voltage proportional to the weight flow rate of air taken into an engine, means for generating a sawtooth wave voltage which is synchronized with the working cycle of the engine and whose slope varies in accordance with the rotational speed of the engine, pulse generating connected in circuit with said two means for comparing the output voltages of said two means to produce a pulse corresponding to the quantity of fuel required for each cylinder of the engine per operating cycle thereof, and at least one electromagnetic valve connected in circuit with said pulse generating means and operable in response to said pulse generated by said pulse generating means, wherein the first mentioned generating means includes an air flow rate-voltage transducer for generating an output voltage directly proportional to the weight flow rate of the air taken into the engine, a temperature coefficient multiplier connected in circuit with said air flow rate-voltage transducer for generating an output voltage representative of the output voltage of said air flow rate-voltage transducer modified in accordance with the temperature of the air induced, an atmospheric pressure detector connected in circuit with said temperature coefficient multiplier for correcting the output voltage of said temperature coefficient multiplier in accordance with the value of the atmospheric pressure and generating an output voltage, and an air throttle valve opening coefficient multiplier connected in circuit with said atmospheric pressure detector for correcting the output voltage of said atmospheric pressure detector in accordance with the opening of said air throttle valve and generating an output signal to said signal to said cOmparator, and wherein said temperature coefficient multiplier comprises a bimetal adapted to make a predetermined amount of mechanical displacement with a change in temperature, and an electrical resistor connected with said bimetal strip whose resistance value changes in accordance with the mechanical displacement of said bimetal strip, whereby the output voltage of said air flow rate-voltage transducer is corrected in accordance with a change in the resistance value of said electrical resistor to produce an output voltage. 